COVID antibody test results hard to interpret, local health experts say

COVID antibody test results hard to interpret, local health experts say

TUCSON, Ariz. (KOLD News 13) - State health leaders are reporting the highest percentage of positive COVID antibody tests since the pandemic began. About 40 percent of serology tests have came back positive for the week of Jan. 17, according to the Arizona Department of Health Services. An antibody test, also known as serology testing, uses a person’s blood to reveal whether they’ve had COVID-19 in the past.

Local health experts said, while the number might be high, they are not concerned. El Rio’s HIV Infectious Disease Clinic Medical Director Dr. Sudha Nagalingam said the test still has many unknowns.

“You may have had severe coronavirus infection and you might not have had an autoimmune response based on your body’s own immunological status,” she said.

Dr. Nagalingam said some people’s COVID antibodies may not show up at all on the serology test.

“I think I would put the serology test results in the interesting but not necessarily useful category of information,” said Dr. Joe Gerald, the University of Arizona Associate Professor of Public Health Policy and Management.

Dr. Gerald said researchers don’t have much information about the people being tested or how long antibodies last which makes the data hard to interpret.

“It’s very difficult when looking at that 40 percent positivity number. What does it mean for Arizona?” he said.

He said the rate is likely high because the people getting tested suspect they’ve had COVID in the past and therefore have a positive test result.

“There could be reasons people seek a serology tests and their probability of being positive is much higher than the population,” he said.

Arizona’s antibody test positivity rate has grown and is about 30 percent higher than it was in the fall of last year,” he said.

“There’s just a lot more COVID out there so more Arizonans have become sick and recovered,” he said. “As part of the recovery process, they have developed antibodies.”

He said he believes the upward trend is accurate but doesn’t think the percentage is an exact reflection of how many Arizonans have had the virus. This past week the state reported about 2,200 positive antibody tests out of 6,350 people, according to AZDHS.

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